The output of the model is not correct even for firing angle between 0 and 90. There are two reasons why the model is not showing expected behavior:
1) The output of "Pulse Generator" block is not connected in the right order to the thyristors. The pulse ordering in the pulse train corresponds to the natural order of commutation of a three-phase thyristor bridge. This order is same as the order generally used for numbering of thyristors in a three-phase bridge, 1/3/5 for the upper half and 4/6/2 for the lower half. You need to connect the appropriate gate pulse to the corresponding thyristor. For more information on the output order of "Pulse Generator" block, refer the following link:
https://www.mathworks.com/help/physmod/sps/powersys/ref/pulsegeneratorthyristor.html
2) The snubber circuit parameters for each thyristor in the "Block Parameters" dialog box are not appropriate. The values given make it difficult for the thyristors to be switched at the right instant. If you are using this model just for the purpose of simulation, you can give very high values for these parameters to get the desired output. You can try "Rs = 1e+5 Ohms" and "Cs = inf" as an example.
